Removal of particles and other contaminants from solid-state surfaces is a major problem in integrated circuit manufacture. Integrated circuit manufacture includes, but is not limited to, production of semiconductor wafers, printed circuit boards, component packaging, and the like. As the trend to miniaturize electronic devices and components continues, and critical dimensions of circuit features become ever smaller, the presence of even a minute foreign particle on a wafer substrate during processing can cause a fatal defect in the circuit. Similar concerns affect other elements used in the manufacturing process, such as photomasks and reticles.
Various methods are known in the art for stripping and cleaning foreign matter from the surfaces of wafers and masks, while avoiding damage to the surfaces themselves. For example, U.S. Pat. No. 4,980,536 to Asch et al., whose disclosure is incorporated herein by reference, describes a method and apparatus for removal of particles from solid-state surfaces by laser bombardment. U.S. Pat. Nos. 5,099,557 and 5,024,968 to Engelsberg, whose disclosures are also incorporated herein by reference, describe methods and apparatus for removing surface contaminants from a substrate by high-energy irradiation. The substrate is irradiated by a laser with sufficient energy to release the particles, while an inert gas flows across the wafer surface to carry away the released particles.
U.S. Pat. No. 4,987,286 to Allen, whose disclosure is likewise incorporated herein by reference, describes a method and apparatus for removing minute particles (even sub-micron particles) from a surface to which they are adhered. An energy transfer medium, typically a fluid, is interposed between each particle to be removed and the surface. The medium is irradiated with laser energy, and absorbs sufficient energy to cause explosive evaporation, thereby dislodging the particles.
U.S. Pat. No. 5,023,424 to Vaught, whose disclosure is incorporated herein by reference, describes a method and apparatus for using laser-induced shock waves to dislodge particles from a wafer surface. A particle detector is used to locate the positions of particles on the wafer surface. A laser beam is then focused at a point above the wafer surface near the position of each of the particles, in order to produce gas-borne shock waves with peak pressure gradients sufficient to dislodge and remove the particles.
U.S. Pat. No. 5,961,732 to Patrin et al., whose disclosure is incorporated herein by reference, describes a method for forming a cryogenic aerosol by expanding a pressurized liquid or liquid/gaseous stream of one or more cryogens through a nozzle into a process chamber. The expansion and/or evaporation causes cooling of the cryogens, leading to formation of a stream of solid aerosol particles. The aerosol is directed at a substrate in order to remove contaminants from the surface.
U.S. Pat. No. 6,295,999 to Bran, whose disclosure is incorporated herein by reference, describes a method for cleaning semiconductor wafers, by using megasonic energy to agitate cleaning fluid applied to the wafer. A source of energy vibrates an elongated probe, which transmits the acoustic energy into the fluid. In one arrangement, fluid is sprayed onto both sides of a wafer while a probe is positioned close to an upper side of the wafer. In another arrangement, a short probe is positioned with its end face close to the surface of a wafer, and the probe is moved over the wafer as it rotates.